This invention relates to a novel radiant electric heater construction especially adapted for use with top surface cooking appliances and more particularly to a combination of novel component parts in said type devices which can effectively serve to replace the customary construction.
Radiant electric heaters intended for top surface cooking appliances now employ "microporous" type thermal and electric insulation which can be molded or otherwise formed to provide the base component in said device when generally supported in a metal dish. Descriptions of said customary radiant electric heater construction can be found in U.S. Pat. No. 5,471,737, U.S. Pat. No. 5,512,731 and U.S. Pat. No. 5,517,002 which all include a requirement for said type insulation material in order to avoid overheating during device operation. A still further description for preparation of a satisfactory microporous insulation of this type can be found in U.S. Pat. No. 5,556,689 which includes a requirement for "a very high specific surface area" of the finely divided metal oxides being employed in order to achieve satisfactory thermal insulation.
The above described thermal insulation remains relatively expensive due to costs of preparation including needed raw materials, processing requirements and still other factors limiting availability. Thus, a preparation of suitable microporous insulation according to the foregoing references can involve elaborate processing techniques such as gel formation, controlled precipitation and fume deposition in order to control average particle size less than 100 nanometers. It would be desirable, therefore, to replace conventional microporous insulation now being used in radiant electric heaters by means which are far less costly as well as far more readily available. In doing so, it has now been discovered that fused silica of the type conventionally produced in a rotary electric arc furnace (such as disclosed in U.S. Pat. No. 4,217,462) and thereafter mechanically reduced by conventional means to produce a suitable particle size provides a satisfactory means of thermal and electric insulation for this product application. It remains only required with said substituted fused silica insulation to further include metal heat shield means in a manner to be disclosed hereinafter for a satisfactory retention of heat within the final device during its operation.
It is an important object of the present invention, therefore, to provide a radiant electric heater employing a novel combination of component parts.
It is another object of the present invention to provide a novel radiant electric heater employing fused silica particulates as the thermal and electrical insulation means in combination with operatively associated heat shield means.
Still another object of the present invention is to provide a novel preparation means for the particular fused silica material being employed in the disclosed heater device.
These and still further objects of the present invention will become more apparent upon considering the following detailed description of the present invention.